So I suppose the question becomes, isn't that what 3e did to earlier editions? And in the process made the imbalance that certainly existed in 1e and BECM and 2e significantly worse than before?
Arguably, if you assume that all the myriad restrictions older editions placed on casters were faithfully implemented by DMs and not circumvented by clever play... in an era that is famed for every DM running the game differently.

...something 5e, I think unironically, also strives for.
One thing I remember hearing a lot when 3.0 was new was "this is just like a lot of my old variants!" ...I didn't find that true for much (OK, I confirmed crits, that was about it), but I heard it a lot.
Anyway, making the balance perfect might not be possible. Making it better - because it WAS better in all editions prior to 3e - is clearly do-able in the mechanical sense. It won't happen because WorC appear determined never to do anything to upset that part of the fanbase determined to have casters retain the power imbalance in their favour that developed over time - an ievitably when every edition except 4e has increased the power of casters significantly while not doing the same for other classes.
Perfect balance is impossible, IMHO, because balance is aspirational, you can always add new choices that are meaningful and viable and don't obviate any existing choices... it just gets harder and harder to do! By the same token, better balance is always possible, in well-balanced games, too, not just badly-balanced ones like D&D.
The TSR era had some balancing factors built in, on paper, but the attitude it had was very much to let DMs do what they liked, so whether those factors made a difference depended on the individual DM.
3e didn't just reduce or eliminate those balancing factors, it produced a community that was willing to set RaW above the DMs' ancient prerogative to change and overrule the rules. (Even tho 3.0, itself, explicitly called out a white-wolf-style 'Rule 0,' the community attitude was still that, RaW were a higher order and 'that's a house rule' was dismissive, or that, for instance, house rules had better be pinned down before characters are built, or the DM was bing somehow unfair.)
4e of course, balanced the classes to a much greater degree than 3e or TSR eds, and did so without resorting to punitive measures or DM fiat. 5e helpfully reversed all that. Well, 5e didn't reverse removing restrictions from casters.